Semiconductor sensor chip and method for producing the chip, and semiconductor sensor and package for assembling the sensor

Abstract

The present invention is a method of making an acceleration sensor chip. The sensor chip is prepared from a SOI wafer having a silicon substrate, a SiO 2 layer and a silicon thin film. A dopant is ion implanted at a position corresponding to a semiconductor strain gauge on the silicon thin film to form a diffusion resistor, and for forming devices necessary for circuit construction on said silicon thin film. A protective film is provided on the entire surface of the wafer, and a plurality of through holes penetrating the silicon thin film are formed by patterning and etching to make a weight part and a beam part connected to a support frame part on the periphery. The SiO 2 layer under the weight part and the beam part is removed by wet etching to form the through holes, while leaving the protective film in place. The protective film is removed and a resist coated over the entire surface of the wafer. A slit for dividing the chip is formed part way through the wafer by dicing. The resist is removed by ashing with an O 2 plasma and the chip is divided by concentrating a stress on the slit.

What is claimed is:  
     
       1. A method of making an acceleration sensor chip comprising: 
       (a) a step for preparing a SOI wafer comprising a silicon substrate, a SiO 2  layer and a silicon thin film;  
       (b) a step for ion implanting a dopant at a position corresponding to a semiconductor strain gauge of said silicon thin film to form a diffusion resistor, and forming devices necessary for circuit construction on said silicon thin film;  
       (c) a step for providing a protective film on the entire surface of said wafer, opening a plurality of through holes penetrating said silicon thin film by patterning and etching, and forming a weight part and a beam part connected to a support frame part on the periphery;  
       (d) a step for removing said SiO 2  layer under said weight part and said beam part by wet etching for forming said plurality of through holes while retaining said protective film;  
       (e) a step for removing said protective film;  
       (f) a step for coating a resist over the entire surface of said wafer;  
       (g) a step for forming a slit by dicing for dividing said chip while retaining a small thickness of said wafer;  
       (h) a step for removing by ashing said resist on said wafer by an O 2  plasma; and  
       (i) a step for dividing said chip by concentrating a stress on said slit.  
     
     
       2. A method of making an angular acceleration sensor chip comprising: 
       (a) a step for preparing a SOI wafer comprising a silicon substrate, a SiO 2  layer and a silicon thin film;  
       (b) a step for ion implanting a dopant at a position corresponding to a semiconductor strain gauge of said silicon thin film to form a diffusion resistor, forming a magnetic thin film at a position corresponding to a weight part, forming a detection coil surrounding said magnetic thin film, and forming devices necessary for circuit construction on said silicon thin film;  
       (c) a step for providing a protective film on the entire surface of said wafer, opening a plurality of through holes penetrating said silicon thin film by patterning and etching, and forming a beam part connecting to said weight part and a support frame part remained on the periphery;  
       (d) a step for removing said SiO 2  layer under said weight part and said beam part by wet etching for forming said plurality of through holes while retaining said protective film;  
       (e) a step for removing said protective film;  
       (f) a step for coating a resist over the entire surface of said wafer;  
       (g) a step for forming a slit by dicing for dividing said chip while retaining a small thickness of said wafer;  
       (h) a step for removing by ashing said resist on said wafer by an O 2  plasma; and  
       (i) a step for dividing said chip by concentrating a stress on said slit.  
     
     
       3. The method of  claim 1 , wherein the dopant is selected from boron and phosphorous. 
     
     
       4. The method of  claim 1 , the device necessary for circuit construction comprising at least one device selected from an adjustment circuit, an amplifier circuit, a terminal and wiring. 
     
     
       5. The method of  claim 2 , wherein the dopant is selected from boron and phosphorous. 
     
     
       6. The method of  claim 2 , the device necessary for circuit construction comprising at least one device selected from an adjustment circuit, an amplifier circuit, a terminal and wiring. 
     
     
       7. A method of making an acceleration sensor chip comprising: 
       a step for providing SOI wafer comprising a first layer of support substrate, an insulating second layer and a silicon thin film third layer;  
       a step for forming a plurality of cutouts of a same width on said third layer to form a sensor structure having a beam part and a weight part for displacing said beam part which are separated from each other;  
       a step for forming a circuit part connected electrically to said sensor structure in the periphery of said third layer;  
       a step for removing said second layer located beneath said sensor structure to make said beam part and said weight part provided on said sensor structure displaceable.  
     
     
       8. A method of making an acceleration sensor chip for constructing a sensor structure on a third layer provided on a first layer of support substrate through an insulating second layer, comprising: 
       a first step for forming a plurality of cutouts of a same width on said third layer to form a detection surface of said sensor structure having a beam part and a weight part for displacing said beam part which are separated from each other;  
       a second step for filling said plurality of cutouts of said same width of said sensor structure with a sealing agent to flatten the surface of said third layer including said sensor structure;  
       a third step for forming a circuit part connected electrically to said sensor structure in the periphery of said surface-flattened third layer; and  
       a fourth step for removing said sealing agent filled in said plurality of cutouts of said same width and removing said second layer located beneath a detection surface of said sensor structure to make said beam part and said weight part provided on said detection surface of said sensor structure displaceable.  
     
     
       9. The method of  claim 8 , further comprising: 
       a fifth step for coating a protective film on the surface of said third layer including said sensor structure after said fourth step, forming a slit in said protective film-coated third layer, and dicing said sensor chip at said slit, and  
       a sixth step for removing said protective film of said third layer after dicing.  
     
     
       10. The method of  claim 8 , wherein in any one of said first step to said fourth step, a film smaller in thermal expansion coefficient than material of said first layer is formed on a backside of said first layer. 
     
     
       11. The method of  claim 8 , wherein said same width of said plurality of cutouts formed on said sensor structure is 2 μm or less. 
     
     
       12. The method of  claim 8 , wherein said substrate comprising said first layer, said second layer and said third layer, is an SOI (silicon-on-insulator) wafer, or a wafer having polysilicon formed as said third layer on a single crystal silicon substrate through an insulation layer.